SOURCE SIDE ASYMMETRICAL PRECHARGE PROGRAMMING SCHEME

摘要

A method for programming NAND flash cells to minimize program stress while allowing for random page programming operations. The method includes asymmetrically precharging a NAND string from a positively biased source line while the bitline is decoupled from the NAND string, followed by the application of a programming voltage to the selected memory cell, and then followed by the application of bitline data. After asymmetrical precharging and application of the programming voltage, all the selected memory cells will be set to a program inhibit state as they will be decoupled from the other memory cells in their respective NAND strings, and their channels will be locally boosted to a voltage effective for inhibiting programming. A VSS biased bitline will discharge the locally boosted channel to VSS, thereby allowing programming of the selected memory cell to occur. A VDD biased bitline will have no effect on the precharged NAND string, thereby maintaining a program inhibited state of that selected memory cell.